Radio position finder



Dec. 26, 1961 P. C. GAUDILLERE RADIO POSITION FINDER Filed April 19,1956 3 Sheets-Sheet 1 R3,, 1; RECEIVER RECEIVER mmsnmea' SHAPING snmussfglmrs 5 523 10 1 P 6 LS COINCIDENCE R 1; E R28 DETECTOR v I t I: I Z Z3 2131 3 DC! (AuxuLARYsmnAL) RECENER 5 RECE'VER Raceway: mm 5mm snow la28 SIGNALS 2 comcmENcE unsc'roa L TIME L MEASURE fgfir'lmguu m-3" 1mmsmmn if MODULATOR TRANSMITTER M nonuunon INVENI'OK Rz'erre LIaudfQ'audz'llere A TITORNEYS Dec. 26, 1961 P. c. GAUDILLERE RADIO POSITIONFINDER 3 Sheets-Sheet 2 Filed April 19, 1956 mm 5580a 5 LB QEH 5m 533mmTl ll W Eu a 3 35 II I! ll m E Q II II Pa 2 ,amaslllll a .z on Illlllll,amp

N P 3. .85 II E Hunt \S E Q 5 Dec. 1961 P. c. GAUDILLERE 3,015,097

RADIO POSITION FINDER Filed April 19, 1956 3 Sheets-Sheet 3 HEEQE CAiUDEGap/44:12:

'l' ited States atent The present invention relates to a radio method ofde V termining the position of a mobile point.

It is known from US. Patent No. 2,727,231 of December 13, 1955, toprovide, in'a systern for determining the position of a receiving pointrelative to spaced transmitters, at least one pair of spacedtransmitters for emitting a signal from each, the signals emitted by thetransmitters of each pair having ditferent frequencies very close to oneanother and of such values that the velocity of propagation of the wavesin kilometers per second divided by the sum of the frequencies in cyclesper sec-' ond is greater than the distance in kilometers between saidtwo transmitters of each said pair, whereby an isophase line is createdwhich constitutes the locus of the points atwhich said two signals arein phase and which moves from one of said transmitters to the other,only one such line existing at any given instant, phase measuringmeansfor detecting the passage of such isophase line through a known pointfixed in position, means for emitting an initial signal from a point ofknown position, at the moment of such passage, additional phasemeasuring means for detecting the passage of said isophase line throughsaid receiving point, andtime measuring means for measuring the time lagbetween the reception of said initial signal at said receiving point andthe passage of said isophase line through said receiving point.

In other terms, it is known to determine one element of position data ofa mobile point M by means of brief signals which are emitted by fixedtransmitters A and B and have periods T and T which are different butclose to each another. a

It has also been proposed, in US. Patent No. 2,850,729

of September 2, 1958, to obtain one curvilinear co-ordi-.

nate of a mobile point by measuring the interval of time between thepassages at this point of two isoph-ases emitted by two pairs oftransmitters, the second curvilinear coordinate of the mobile pointbeing obtained by'means of two other isophases generated by said fourtransmitters differently combined to form two other pairs. This method,however, also requires two interval measurements.

For this purpose a system is used comprising units situated at points A,B, M and at a reference point,

Patented Dec. 26, 1961 V According to this known method, the completedetermination of the position of a mobile point on a surface, such asthe ground surface, requires a second curvilinear c'o-ordinate to beobtained and in consequence the use of another pairot transmittingstations which permit defining a'second series of curves of position.The complete position determination also requires a second time intervalmeasurement i.

The object of the present invention is to provide a method which, byusing a similar system and effecting only one time interval measurement,permits obtaining the two curvilinear 'co-ordinates required'in thecomplete determination of the position of the mobile point.

In the method according to the present invention, one of the signalshaving periods T and T is utilized in the form of a short signal and theother in the form of a broad signal whose duration equals or is slightlygreater than T T where T is supposed greater than T According to apreferred mode of carrying out the invention the signals are emitted byA and B in any form on distinct carrier frequencies modulated at periodsT and T and are transformed in the receivers into short F. The signalsemitted by A and B are received in coincidence at instant I, at one ofthe points M and F, this point emit-ting at this instant I a signal Z,and the signals-emitted by A. and B being received in coincidence atinstant I at'the other of the two points M and F, at which point thesignal Z is received at instant I and the interval of time i betweeninstants I and I is measured. Determination of this interval of timeperm-its obtaining a curvilinear coordinate of the mobile point. 1

The system therefore comprises, in addition to the transmitting stationsA and B, an auxiliary station disposed at one of the points M and F andacting as a receiver, coincidence detector and transmitter of the signalZ, and a control or position-determining station disposed at the otherof the points M'- and -F and acting as a receiver for the signal Z,coincidence detector and time interval measurer. When the controlstation is situated at M, a subjective position determination might V besaid tube effected, the auxiliary station being at F;

and broad pulses respectively. k V

According to one feature ofthe invention, the measurementor value of theratio V i Y 1 provides, in respect of the point whose position is to bedetermined: by its integerpart, a first curvilinear coordinate in aseries of hyperbo'lae having feel A and B,

and, by its fractional part, 'a secondcurvilinear co-ordinate in thesecond series of conics whose foci are A and the third fixed point.

In a first embodiment of the invention, the control station is fixed,the auxiliary station is on the mobile point, and the second series is aseries of ellipses whose foci are A and the point of the auxiliarystation.

' The measurement of the time interval 1 may be effected by any knownmethod, for example by means of an electronic counter which receivespuises of frequency or by means of a cathode-ray tube subjected to twolinear sweep voltages. V

Further features and advantages of the invention will be apparent fromthe ensuing description with reference to the accompanying drawings towhich the invention is in no way limited.

In the drawings:

FIG. 1 is a diagram illustrating the principle of the invention; V

FIG. lAis a series of graphs illustrating-the operation of the systemwhich is one object of 'the invention;

FIG. 2 is a diagram relating to objective position determination; V

FIG. 3 is a diagram relating to subjective position determination: V

FIG. 4 is a block diagram of a system according to an embodiment of theinventiom'and FIGURE 4a is a block diagram illustrating a portion of thesystem shown in FIGURE 4, according to another embodiment of theinvention.

In a general way, themethod of position determination of the inventionmay be described as follows:

(a) Two transmitters A and B are disposed at two known fixed points(FIG. 1) and emit signals whose periods T and T are different but neartoone another.

(7;) Disposed at each of two points P and P one of these points beingfixed and of known position and the other being the point whose positionis to be determined-are two receivers R R (FIG. 1A, graphs 1 and 2); andR R (FIG. 1A, graphs 4 and 5); which receive the signals fromtransmitters A and B and detect the instants I (FIG. 1A, graph 3); and I(FIG. 1A, graph 6); when these two signals reach them in coincidence.

(c) A transmitter E emits at point P a signal Z at instant I (FIG. 1A,graph 3).

(d) At point P a receiver R receives the signal Z (FIG. 1A, graph 7);and a'measuring device measures (FIG. 1A, graph 8); the time interval ibetween the instant I and the instant I of reception of the signal Z.

(e) According to the essential feature of the invention, at the instantwhen the signals emitted by A and B are compared for determining theircoincidence, one of these signals (for example signal A) is in the formof short pulses and the other (signal B) is in the form of signals ofduration equal to or slightly greater than T -T (FIG. 1A, graphs 1, 2,4, 5).

This condition may be satisfied in the following way: the signals areemitted by A and B on distinct carrier frequencies in any form modulatedat periods T and T by any known method, for example:

Short pulse modulation.

Sinusoidal amplitude modulation.

Sinusoidal frequency modulation.

Telegraph modulaton.

Telegraph frequency shift modulation.

In this case the receivers R A and R comprise circuits of conventionaltype receiving and detecting separately the signals of frequencyAssuming that T and T are commensurable, let it be supposed that whereinN is an integer.

This gives:

and the phenomenon has the periodicity:

1 2 T-NT (N+ l) T T2 It will also be assumed that there is an instantwhen T and T are emitted simultaneously at A and B; this coincidencerecurs with period T. Each of these instants of coincidence is taken aszero in time. The instants of emission are therefore (n being an integernumber):

at A 0, T 2T nT; with n N at B 0, T2, 2T2 "T2 with Il- N T1-Tg beingsmall relative to T the above-mentioned coincidence always occurs withsuflicient approximation. A receiversituated a distance r from A and rfrom B, receives the signals A at instants wherein c designates thespeed of propagation of the electromagnetic waves; on account of theappreciable duration (equal to T -T of the signals B, the same receiverreceives the signals B between instants Hyperbolae defined by r -r =nc(T -T are constructed for all the integer values of n (positive andnegative between Hereinafter, the term channel is used for the areacomprised between two consecutive hyperbolae, i.e. two hyperbolaecorresponding to two consecutive values of n; the area between the twohyperbolae corresponding to n-1 and n is called the nth channel.

and

H TV- has been chosen for the maximum value of r in the area to becovered.

All receivers placed in the nth channel detect the coincidence betweenthe instants nT and (n+l)T If the point P is in the nth channel at adistance r from A and if the point P is in the nth channel at a distancer from A and at a distance r from P the transmitter E situated at Pemits the signal Z at instant ll=ntrl+ This signal is received at P atinstant Coincidence occurs at P at instant The interval of time betweenthe instant I of coincidence and the instant I of reception of thesignal Z is measured at P T; has been chosen greater than the maximum ofin the entire area to be covered.

The value 1 provides:

(1) The value of Q=n--n' where Q is the integer part of the quotient of1' divided by T This value permits locating the point of unknownposition in one of the channels constituted by the above-mentionedseries of hyperbolae.

(2) The value of R 6 T1 being the fractional part of theabove-mentioned-quotient. This value permits locating the point inquestion in a chanwhich shows that the foci are A and P nel of a secondseries of curves, as will be explained hereinbelow. v

A single measurement of an interval of time therefore permitsdetermining the position of a point on a surface.

This process may be used for effecting an objective positiondetermination or a subjective position determination.

OBJECTIVE POSITION DETERMINATION P being considered as the point whoseposition is to be determined and P the fixed point of known position,the system comprises (FIG. 4) the transmitting station A having amodulator M of period T and a transmitter E of signals A, and thetransmitting station B having a modulator M of period T and atransmitter E of signals B.

The system further comprises:

(1.) The auxiliary station which is disposed at the mobile point P andcomprises: a receiving station R receiving signals emitted by A; ashaping device F transforming the signals into short signals A; areceiving station R receiving the signals emitted by B; a shaping deviceF 3 transforming these signals into broad signals B; a coincidencedetector DC comprising a coincidence tube whose grids receive thesignals A and B and whose plate generates at instant i of coincidencethe signal Z; a transmitter E emitting this signal Z.

(2) The control station which is disposed at'the fixed point P an'dwhich comprises: a receiving station R receiving the signals emitted byA; a shaping device F transforming these signals into short signals A; areceiving station R receiving the signals emitted by B; a shaping deviceF transforming these signals into broad signals B; a coincidencedetector DC similar to the device DC and detecting the coincidence I areceiving station R receiving the signal Z at instant I a time measuringapparatus MT measuring the time interval i between I and I It has beenseen that iis equal to In the present case, the values r AP and n(number of the channel pertaining to P are unknown; the values r =AP and11 (number of the channel pertaining to P are known; the value r=P P isunknown.

The value or" Q=nn' where Q is the integer partof the quotient of idivided by T provides the value of n and thus permits determining forthe point P the number of the channel in the series of hyperboiae havingfoci A, B (see FIG. 2). 1

The value of being the fractional pait of the above-mentioned quotient,defines an ellipse whose equation may be written The geographicpositionof P is thus completely defined by the single measurement of iwhich provides the parameter of the hyperbola and the parameter of theellipse.

devices:

(1) Electronic counter As shown diagrammatically in FIGURE 4, the time,2 Cathode-ray tuba As shown diagrammatically in FIGURE 4a the timemeasuring apparatus MT may consist of a cathode-ray tube is subjected totwo linear sweep voltages in a similar manner to a television screentube. The sweeping of the image is started by the signal I and the linesweeping is started by the signals A received at the control station PThe signalZ received from the mobile point renders the spot luminous.Thus a mobile point situated in the nth channel causes a luminous spotto appear on the nth line of the screen at a distance KR from the originof this line, K being a constant It is possible, therefore, to determinesimultaneously the position of several mobile points. It is furthermorepossible to replace the linear sweeping of ,the television type bynon-linear sweeping so that the position of the luminous points appearson a map which is superimposed on the screen and is devoid of excessivedeformation.

The above-described device generally gives for any measurement of 2' twopositions of the mobile point since the ellipse intersects a hyperbolicchannel at two points. This ambiguity is easily settled in mos-tproblems of teleguiding where the approximate position of the mobilepoint is known. 'It is generally knownon which side of the straight lineAB the mobile point is situated and advantageously the station P isdisposed in the region of this line, the two points of intersectionbeing then symmetrical relative to AB. If the point P is situated in theregion of A, the ellipses become circles and a direct measure of thedistance is obtained. If the point P is situated in the region of B, theellipses and the hyperbolae have common foci and intersect one anotherat right angles; this device is of particular advantage as concerns theprecision of the position determination.

'SUBJECTIVE POSITION DETERMINATION In this case it is P which is themobile point Whose position is to be determined; the auxiliary stationis, then, disposed at the fixed point P and the control station at themobile point P In other words, with this arrangement the disposition ofthe various units of the system at A, B, P and P is identical to thatdescribed in respect of objective position determination. In this casein the formula:

being the functional. part of the above-mentioned quotient, defines ahyperbola whose equation may be written:

r-r =cR'-r which shows that the foci are A and P The geographic positionof P is thus completely defined by the simple measurement of i whichprovides the parameter of the hyperbola having foci A, B and theparameter of the hyperbola having foci A, P

The position data thus obtained depends on the position of the auxiliarystation P if it is desired to obtain the position of the mobile point bytwo co-ordinates, the transmitter P must be placed at such position thatthe second hyperbolae intersect the first at angles as near as possibleto right angles throughout the area under consideration. This isobtained by disposing the vectors AB and .AP in such manner that theymake between themselves a straight angle or obtuse angle bounding thiszone. In this arrangement the same methods as those described for thefirst arrangement may be used for measuring i.

The diagram of the system shown in FIG. 4 is valid for both cases ofobjective and subjective position determination with the sole difierencethat in the first case P is mobile and of unknown position and P fixedand of known position, whereas in the second case the situation isreversed.

According to one modification of the invention, in the case of objectiveposition determination the signal Z emitted by the mobile point may beformed by a combination of signals in accordance with a predeterminedcode which permits providing certain information such as the identity ofthe mobile point or its altitude if it concerns an aerial mobile object.In the latter case, for example, the signal 2 could be followed byanother signal Z, the time interval between these two signals being setby a barometric altimeter. The measurement of this time interval at thestation P gives the altitude of the mobile point.

Although specific embodiments of the invention have been liereinabovedescribed, many modifications and changes may be made therein withoutdeparting from the scope of the invention as defined in the appendedclaims.

Having now described my invention what I claim as new and desire tosecure by Letters latent is:

1. Radio method of determining the position of a mobile point relativeto spaced transmitters, comprising the following steps: emitting fromtwo fixed spaced transmitters A and B signals having periods T and Trespectively which are difierent but close to one another, said signalsbeing of any shape and being carried by carrier waves of differentfrequencies modulated at periods T and T receiving said signals at afixed point and at the mobile point whose position is to be determined;at each of said points, transforming one of said signals into a shortsignal and the other signal into a broad signal whose duration is equalto or slightly greater than T -T and determining the instant ofcoincidence of these two transformed signals; emitting an auxiliarysignal at the instant of coincidence at one of said points from anauxiliary station located at this point; receiving said auxiliary signalat a control station located at the other of said points; measuring atsaid control station the time interval i between the instant when thetwo signals are in coincidence at said control station and the instantof reception of said auxiliary signal at said control station; computingthe integer part of the quotient to obtain a first curvilinearcoordinate of said mobile point in a series of hyperbolae whose foci areA and B, and computing the fraction part of said quotient 1 to obtain asecond curvilinear co-ordinate of said mobile point in a series ofcomics whose foci are A and said fixed point.

2. Radio method of determining the position of a mobile point relativeto spaced transmitters, comprising the following steps: emitting fromtwo fixed spaced transmitters A and B signals having periods T and Trespectively which are different but close to one another, said signalsbeing of any shape and being carried by carrier waves having diiierentfrequencies modulated at periods T and T receiving said signals at afixed point and at the mobile point whose position is to be determined;at each of said points, transforming one of said signals into a shortsignal and the other signal into a broad signal whose duration is equalto or slightly greater than T -T and determining the instant ofcoincidence of these two transformed signals; emitting an auxiliarysignal at the instant of coincidence at said mobile point from anauxiliary station located at said mobile point; receiving said auxiliarysignal at a control station located at the fixed point; measuring atsaid control station the time interval i between the instant when thetwo signals are in coincidence at said control station and the instantof reception at said control station of said auxiliary signal; computingthe integer part of the quotient to obtain a first curvilinearco-ordinate of said mobile point in a series of hyperbolae whose fociare at A and B, and computing the fraction part of said quotient 1 toobtain a second curvilinear co-ordinate of said mobile point in a seriesof ellipses whose foci are at A and said fixed point.

3. Radio method of determining the position of a mobile point relativeto spaced transmitters, comprising the following steps: emitting fromtwo fixed spaced transmitters A and B signals having periods T and Trespectively which are difierent but close to one another, said signalsbeing of any shape and being carried by carrier waves having differentfrequencies modulated at periods T and T receiving said signals at afixed point and at the mobile point whose position is to be determined;at each of said points, transforming one of said signals into a shortsignal and the other signal into a broad signal whose duration is equalto or slightly greater than T T and determining the instant ofcoincidence of these two transformed signals; emitting an auxiliarysignal at the instant of coincidence at said fixed point from anauxiliary station located at said fixed point; receiving said auxiliarysignal at a control station located at said mobile point; measuring atsaid control station the time interval 1' between the instant when thetwo signals are in coincidence at said control station and the instantof reception at said control station of said auxiliary signal; computingthe integer part of the quotient to obtain a first curvilinearco-ordinate of said mobile point in a series of hyperbolae whose fociare at A and B, and computing the fractional part of said quotient saidsignals into short signals and broad signals respectively, the lattersignals having a duration equal to or slightly greater than T T meansfor determining the instant of coincidence of these two transformedsignals, and means for emitting an auxiliary signal at this instant; acontrol station located at a second point, said mobile point being oneof said first and second points; at said control station, means forreceiving said signals having periods T and T 'and said auxiliarysignal, means for transforming said signals having periods T and T intoshort signals and broad signals respectively, the latter signals havinga duration equal to or slightly greater than T T and means for measuringthe integer part and means for measuring the fraction part of thequotient 1 i being the time interval between the instant when saidauxiliary signal is received at said control station and the instant ofcoincidence at said control station of said two signals having periods Tand T 5. In an installation for the vradio determination of the positionof a mobile point relative to spaced transmitters; two fixed spacedtransmitters A and B for emitting respectively signals having periods Tand T which are different but close to one another; an auxiliaryreceivertransmitter located at said mobile point; in saidreceivertransmitter, means for receiving said signals having periods Tand T means for transforming said signals into short signals and broadsignals respectively, the latter signals having a duration equal to orslightly greater than T -T means for determining the instant ofcoincidence of these two transformed signals and means for emitting atthis instant an auxiliary signal; a control station located at a fixedpoint; at said control station, means for receiving said signals havingperiods T and T and said auxiliary signal, means for transforming thesignals having periods T and T into short signals and broad signalsrespectively, the latter signals having a duration equal to or slightlygreater than T T and means for measuring the integer part and means formeasuring the fraction part of the quotient 1 i being the time intervalbetween the instant when said auxiliary signal is received at saidcontrol station and the instant of coincidence of the transformedsignals having periods T and T at said control station.

6. In aninstallation for the radio determination of the position of amobile point relative to spaced transmitters; two spaced transmitters Aand B for emitting respectively signals having periods T and T which areditferent but broad signals respectively, the latter signals having aduration equal to or slightly greater than T -T means for determiningthe instant of coincidence of these two transformed signals and meansfor emitting at this instant an auxiliary signal; a control stationlocated at said mobile point; at said control station, means forreceiving said signals having periods T and T and said auxiliarysignals, means for transforming the signals having periods T and T intoshort signals and broad signals respectively, the latter signals havinga duration equal to or slightly greater than T -T and means formeasuring the integer part and means for measuring the fraction part ofthe quotient i i being the time interval between the instant when saidauxiliary signal is received at said control station and the instant ofcoincidence of the transformed signals having periods T and T at saidcontrol station.

7. Installation as claimed in claim 4, wherein said measuring meanscomprise an electronic counter fed at a frequency n being aninteger,"the counting of which is started by the reception incoincidence of said signals having periods Ti and T and stopped by thereception of said auxiliary signal.

8. Installation as claimed in claim 4, wherein said measuring meanscomprise a cathode-ray tube subjected to two linear sweep voltages thefield sweep being controlled by the reception in coincidence of thesignals having periods T and T at the control station, the line sweepbeing controlled by the reception at the control station of the signalsemitted by the transmitter A, and the brightness of the spot beingcontrolled by the reception of said auxiliary signal.

References Cited in the file of this patent Hawkins July

